1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2 /* Copyright (C) 2015-2018 Netronome Systems, Inc. */
3
4 #include <linux/delay.h>
5 #include <linux/device.h>
6 #include <linux/jiffies.h>
7 #include <linux/types.h>
8 #include <linux/slab.h>
9 #include <linux/wait.h>
10
11 #include "nfp_cpp.h"
12 #include "nfp6000/nfp6000.h"
13
14 struct nfp_cpp_mutex {
15 struct nfp_cpp *cpp;
16 int target;
17 u16 depth;
18 unsigned long long address;
19 u32 key;
20 };
21
nfp_mutex_locked(u16 interface)22 static u32 nfp_mutex_locked(u16 interface)
23 {
24 return (u32)interface << 16 | 0x000f;
25 }
26
nfp_mutex_unlocked(u16 interface)27 static u32 nfp_mutex_unlocked(u16 interface)
28 {
29 return (u32)interface << 16 | 0x0000;
30 }
31
nfp_mutex_owner(u32 val)32 static u32 nfp_mutex_owner(u32 val)
33 {
34 return val >> 16;
35 }
36
nfp_mutex_is_locked(u32 val)37 static bool nfp_mutex_is_locked(u32 val)
38 {
39 return (val & 0xffff) == 0x000f;
40 }
41
nfp_mutex_is_unlocked(u32 val)42 static bool nfp_mutex_is_unlocked(u32 val)
43 {
44 return (val & 0xffff) == 0000;
45 }
46
47 /* If you need more than 65536 recursive locks, please rethink your code. */
48 #define NFP_MUTEX_DEPTH_MAX 0xffff
49
50 static int
nfp_cpp_mutex_validate(u16 interface,int * target,unsigned long long address)51 nfp_cpp_mutex_validate(u16 interface, int *target, unsigned long long address)
52 {
53 /* Not permitted on invalid interfaces */
54 if (NFP_CPP_INTERFACE_TYPE_of(interface) ==
55 NFP_CPP_INTERFACE_TYPE_INVALID)
56 return -EINVAL;
57
58 /* Address must be 64-bit aligned */
59 if (address & 7)
60 return -EINVAL;
61
62 if (*target != NFP_CPP_TARGET_MU)
63 return -EINVAL;
64
65 return 0;
66 }
67
68 /**
69 * nfp_cpp_mutex_init() - Initialize a mutex location
70 * @cpp: NFP CPP handle
71 * @target: NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
72 * @address: Offset into the address space of the NFP CPP target ID
73 * @key: Unique 32-bit value for this mutex
74 *
75 * The CPP target:address must point to a 64-bit aligned location, and
76 * will initialize 64 bits of data at the location.
77 *
78 * This creates the initial mutex state, as locked by this
79 * nfp_cpp_interface().
80 *
81 * This function should only be called when setting up
82 * the initial lock state upon boot-up of the system.
83 *
84 * Return: 0 on success, or -errno on failure
85 */
nfp_cpp_mutex_init(struct nfp_cpp * cpp,int target,unsigned long long address,u32 key)86 int nfp_cpp_mutex_init(struct nfp_cpp *cpp,
87 int target, unsigned long long address, u32 key)
88 {
89 const u32 muw = NFP_CPP_ID(target, 4, 0); /* atomic_write */
90 u16 interface = nfp_cpp_interface(cpp);
91 int err;
92
93 err = nfp_cpp_mutex_validate(interface, &target, address);
94 if (err)
95 return err;
96
97 err = nfp_cpp_writel(cpp, muw, address + 4, key);
98 if (err)
99 return err;
100
101 err = nfp_cpp_writel(cpp, muw, address, nfp_mutex_locked(interface));
102 if (err)
103 return err;
104
105 return 0;
106 }
107
108 /**
109 * nfp_cpp_mutex_alloc() - Create a mutex handle
110 * @cpp: NFP CPP handle
111 * @target: NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
112 * @address: Offset into the address space of the NFP CPP target ID
113 * @key: 32-bit unique key (must match the key at this location)
114 *
115 * The CPP target:address must point to a 64-bit aligned location, and
116 * reserve 64 bits of data at the location for use by the handle.
117 *
118 * Only target/address pairs that point to entities that support the
119 * MU Atomic Engine's CmpAndSwap32 command are supported.
120 *
121 * Return: A non-NULL struct nfp_cpp_mutex * on success, NULL on failure.
122 */
nfp_cpp_mutex_alloc(struct nfp_cpp * cpp,int target,unsigned long long address,u32 key)123 struct nfp_cpp_mutex *nfp_cpp_mutex_alloc(struct nfp_cpp *cpp, int target,
124 unsigned long long address, u32 key)
125 {
126 const u32 mur = NFP_CPP_ID(target, 3, 0); /* atomic_read */
127 u16 interface = nfp_cpp_interface(cpp);
128 struct nfp_cpp_mutex *mutex;
129 int err;
130 u32 tmp;
131
132 err = nfp_cpp_mutex_validate(interface, &target, address);
133 if (err)
134 return NULL;
135
136 err = nfp_cpp_readl(cpp, mur, address + 4, &tmp);
137 if (err < 0)
138 return NULL;
139
140 if (tmp != key)
141 return NULL;
142
143 mutex = kzalloc(sizeof(*mutex), GFP_KERNEL);
144 if (!mutex)
145 return NULL;
146
147 mutex->cpp = cpp;
148 mutex->target = target;
149 mutex->address = address;
150 mutex->key = key;
151 mutex->depth = 0;
152
153 return mutex;
154 }
155
156 /**
157 * nfp_cpp_mutex_free() - Free a mutex handle - does not alter the lock state
158 * @mutex: NFP CPP Mutex handle
159 */
nfp_cpp_mutex_free(struct nfp_cpp_mutex * mutex)160 void nfp_cpp_mutex_free(struct nfp_cpp_mutex *mutex)
161 {
162 kfree(mutex);
163 }
164
165 /**
166 * nfp_cpp_mutex_lock() - Lock a mutex handle, using the NFP MU Atomic Engine
167 * @mutex: NFP CPP Mutex handle
168 *
169 * Return: 0 on success, or -errno on failure
170 */
nfp_cpp_mutex_lock(struct nfp_cpp_mutex * mutex)171 int nfp_cpp_mutex_lock(struct nfp_cpp_mutex *mutex)
172 {
173 unsigned long warn_at = jiffies + NFP_MUTEX_WAIT_FIRST_WARN * HZ;
174 unsigned long err_at = jiffies + NFP_MUTEX_WAIT_ERROR * HZ;
175 unsigned int timeout_ms = 1;
176 int err;
177
178 /* We can't use a waitqueue here, because the unlocker
179 * might be on a separate CPU.
180 *
181 * So just wait for now.
182 */
183 for (;;) {
184 err = nfp_cpp_mutex_trylock(mutex);
185 if (err != -EBUSY)
186 break;
187
188 err = msleep_interruptible(timeout_ms);
189 if (err != 0) {
190 nfp_info(mutex->cpp,
191 "interrupted waiting for NFP mutex\n");
192 return -ERESTARTSYS;
193 }
194
195 if (time_is_before_eq_jiffies(warn_at)) {
196 warn_at = jiffies + NFP_MUTEX_WAIT_NEXT_WARN * HZ;
197 nfp_warn(mutex->cpp,
198 "Warning: waiting for NFP mutex [depth:%hd target:%d addr:%llx key:%08x]\n",
199 mutex->depth,
200 mutex->target, mutex->address, mutex->key);
201 }
202 if (time_is_before_eq_jiffies(err_at)) {
203 nfp_err(mutex->cpp, "Error: mutex wait timed out\n");
204 return -EBUSY;
205 }
206 }
207
208 return err;
209 }
210
211 /**
212 * nfp_cpp_mutex_unlock() - Unlock a mutex handle, using the MU Atomic Engine
213 * @mutex: NFP CPP Mutex handle
214 *
215 * Return: 0 on success, or -errno on failure
216 */
nfp_cpp_mutex_unlock(struct nfp_cpp_mutex * mutex)217 int nfp_cpp_mutex_unlock(struct nfp_cpp_mutex *mutex)
218 {
219 const u32 muw = NFP_CPP_ID(mutex->target, 4, 0); /* atomic_write */
220 const u32 mur = NFP_CPP_ID(mutex->target, 3, 0); /* atomic_read */
221 struct nfp_cpp *cpp = mutex->cpp;
222 u32 key, value;
223 u16 interface;
224 int err;
225
226 interface = nfp_cpp_interface(cpp);
227
228 if (mutex->depth > 1) {
229 mutex->depth--;
230 return 0;
231 }
232
233 err = nfp_cpp_readl(mutex->cpp, mur, mutex->address + 4, &key);
234 if (err < 0)
235 return err;
236
237 if (key != mutex->key)
238 return -EPERM;
239
240 err = nfp_cpp_readl(mutex->cpp, mur, mutex->address, &value);
241 if (err < 0)
242 return err;
243
244 if (value != nfp_mutex_locked(interface))
245 return -EACCES;
246
247 err = nfp_cpp_writel(cpp, muw, mutex->address,
248 nfp_mutex_unlocked(interface));
249 if (err < 0)
250 return err;
251
252 mutex->depth = 0;
253 return 0;
254 }
255
256 /**
257 * nfp_cpp_mutex_trylock() - Attempt to lock a mutex handle
258 * @mutex: NFP CPP Mutex handle
259 *
260 * Return: 0 if the lock succeeded, -errno on failure
261 */
nfp_cpp_mutex_trylock(struct nfp_cpp_mutex * mutex)262 int nfp_cpp_mutex_trylock(struct nfp_cpp_mutex *mutex)
263 {
264 const u32 muw = NFP_CPP_ID(mutex->target, 4, 0); /* atomic_write */
265 const u32 mus = NFP_CPP_ID(mutex->target, 5, 3); /* test_set_imm */
266 const u32 mur = NFP_CPP_ID(mutex->target, 3, 0); /* atomic_read */
267 struct nfp_cpp *cpp = mutex->cpp;
268 u32 key, value, tmp;
269 int err;
270
271 if (mutex->depth > 0) {
272 if (mutex->depth == NFP_MUTEX_DEPTH_MAX)
273 return -E2BIG;
274 mutex->depth++;
275 return 0;
276 }
277
278 /* Verify that the lock marker is not damaged */
279 err = nfp_cpp_readl(cpp, mur, mutex->address + 4, &key);
280 if (err < 0)
281 return err;
282
283 if (key != mutex->key)
284 return -EPERM;
285
286 /* Compare against the unlocked state, and if true,
287 * write the interface id into the top 16 bits, and
288 * mark as locked.
289 */
290 value = nfp_mutex_locked(nfp_cpp_interface(cpp));
291
292 /* We use test_set_imm here, as it implies a read
293 * of the current state, and sets the bits in the
294 * bytemask of the command to 1s. Since the mutex
295 * is guaranteed to be 64-bit aligned, the bytemask
296 * of this 32-bit command is ensured to be 8'b00001111,
297 * which implies that the lower 4 bits will be set to
298 * ones regardless of the initial state.
299 *
300 * Since this is a 'Readback' operation, with no Pull
301 * data, we can treat this as a normal Push (read)
302 * atomic, which returns the original value.
303 */
304 err = nfp_cpp_readl(cpp, mus, mutex->address, &tmp);
305 if (err < 0)
306 return err;
307
308 /* Was it unlocked? */
309 if (nfp_mutex_is_unlocked(tmp)) {
310 /* The read value can only be 0x....0000 in the unlocked state.
311 * If there was another contending for this lock, then
312 * the lock state would be 0x....000f
313 */
314
315 /* Write our owner ID into the lock
316 * While not strictly necessary, this helps with
317 * debug and bookkeeping.
318 */
319 err = nfp_cpp_writel(cpp, muw, mutex->address, value);
320 if (err < 0)
321 return err;
322
323 mutex->depth = 1;
324 return 0;
325 }
326
327 return nfp_mutex_is_locked(tmp) ? -EBUSY : -EINVAL;
328 }
329
330 /**
331 * nfp_cpp_mutex_reclaim() - Unlock mutex if held by local endpoint
332 * @cpp: NFP CPP handle
333 * @target: NFP CPP target ID (ie NFP_CPP_TARGET_CLS or NFP_CPP_TARGET_MU)
334 * @address: Offset into the address space of the NFP CPP target ID
335 *
336 * Release lock if held by local system. Extreme care is advised, call only
337 * when no local lock users can exist.
338 *
339 * Return: 0 if the lock was OK, 1 if locked by us, -errno on invalid mutex
340 */
nfp_cpp_mutex_reclaim(struct nfp_cpp * cpp,int target,unsigned long long address)341 int nfp_cpp_mutex_reclaim(struct nfp_cpp *cpp, int target,
342 unsigned long long address)
343 {
344 const u32 mur = NFP_CPP_ID(target, 3, 0); /* atomic_read */
345 const u32 muw = NFP_CPP_ID(target, 4, 0); /* atomic_write */
346 u16 interface = nfp_cpp_interface(cpp);
347 int err;
348 u32 tmp;
349
350 err = nfp_cpp_mutex_validate(interface, &target, address);
351 if (err)
352 return err;
353
354 /* Check lock */
355 err = nfp_cpp_readl(cpp, mur, address, &tmp);
356 if (err < 0)
357 return err;
358
359 if (nfp_mutex_is_unlocked(tmp) || nfp_mutex_owner(tmp) != interface)
360 return 0;
361
362 /* Bust the lock */
363 err = nfp_cpp_writel(cpp, muw, address, nfp_mutex_unlocked(interface));
364 if (err < 0)
365 return err;
366
367 return 1;
368 }
369